In distributed computing environments, often there is a need to share computing resources (e.g., files or software applications). One of the most popular examples of a distributed environment with resource sharing is a peer-to-peer (P2P) file sharing community. In a P2P environment, there is no concept of a dedicated centralized server to provide clients with requested resources. Instead, every peer or participant in the system acts as both client and as server, depending upon the context. Users can share heterogeneous resources residing in various platforms and in different policy environments. A P2P-based resource management model can provide higher resource availability due to the distributed nature of P2P computing. In a generalization of the P2P model, resource providers and resource consumers can belong to a multitude of organizations, and each resource provider can define the access policy and service levels for the resources provided, while each service requestor can select the resources based on the access policy and service level.
However, the lack of effective and scalable access control mechanisms has become a serious constraint for broader applications of resource sharing technologies in distributed environments. Considering the dynamism of a large-scale distributed environment, where users and resource providers from different organizations can join and leave the resource sharing communities frequently, the conventional identity-based access control is severely undermined by its inability to scale with the growth of the population of the resource sharing community. Therefore, there is a need to provide an effective and scalable access control mechanism for resource sharing communities encompassing multiple organizations.